The pressurized pen of the related art such as a ball-point pen has often encountered troubles such as failure of the ink to come out smoothly, from the pen tip of a pen refill unit, when used, a run out of the ink, while being used for writing in an upward position, inability to write or leakage of the ink from the rear end portion of the pen refill unit.
In the related art, on the contrary, the pen cylinder of the knock-type ball-point pen is loaded with a pen refill unit having a pen tip at the front end portion of a medium containing tube for containing a medium or ink, and a pressuring pump mechanism for pressurizing the inside of the rear end opening portion of the medium containing tube in that pen refill unit, and this pressuring pump mechanism is associated with a knock mechanism disposed in the rear end portion of the pen cylinder. By the pushing action of the knock rod, the pen refill unit is moved in the axial direction, and the pressuring pump mechanism is actuated to pressurize the inside of the rear end opening portion of the medium containing tube thereby preventing the run out of the ink as described in JP-A-2005-280119 or JP-A-2005-288794.
In the pressuring pump mechanism in the ball-point pen described in JP-A-2005-280119, a rotor for rotating in association with the knock mechanism is disposed to face a cylinder into which the medium containing tube of the pen refill unit is inserted, and a seal ring is interposed between the inner circumference of the cylinder and the outer circumference of the rotor whereas a seal member is interposed between the inner circumference of the cylinder and the outer circumference of the medium containing tube. As a result, the cylinder inside between the two seal portions is used as a compression chamber thereby keeping the sealing property so that the air in the compression chamber may be compressed by the movement of the rotor at the pressurizing time in the knocking operation of the knock mechanism.
In the aforementioned pressuring pump mechanism, however, the seal portion between the outer circumference of the rotor and the inner circumference of the cylinder acts as the rotational contact face on the axis, and the seal portion between the inner circumference of the cylinder and the outer circumference of the medium containing tube acts as a contact face for a sliding contact in the axial directions.
Therefore, the two seal portions slide and rub each other in each knocking operation of the knock mechanism so that they become loose or wear thereby raising problems that the sealing property drops during a long use, that the durability is deteriorated, and that the seal portions have to be formed in a strictly high sizing precision.
In the aforementioned pressuring pump mechanism in another ball-point pen as disclosed in JP-A-2005-288794, the rear end opening portion of a bellows-shaped compression chamber which is made extensible and contractible in axial directions can be sealed at the front end portion of a rotor for rotating in association with the knock mechanism, and a seal member is disposed on the side of a front end opening portion, into which the medium containing tube of the pen refill unit is inserted, so that the sealing property in the compression chamber may be kept at the pressurizing time in the knocking operation of the knock mechanism.
In the aforementioned pressuring pump mechanism, however, the seal portion between the rotor and the rear end opening portion of the compression chamber acts as the rotational contact face on the axis, and the seal portion between the seal member on the side of the front end opening portion of the compression chamber and the medium containing tube acts as a contact face for the sliding contact in the axial directions. Thus, this pressuring pump mechanism has problems like the aforementioned ones of JP-A-2005-280119.